A nonaqueous electrolyte battery in which a charge and a discharge are performed by migration of lithium ions between a negative electrode and a positive electrode has been actively researched as a high energy density battery.
In addition to the use as a power supply for small electronic devices, the nonaqueous electrolyte battery is expected to be utilized also as a medium to large-size power source, such as for in-vehicle applications and stationary applications. The nonaqueous electrolyte battery is required to have excellent life characteristics and high stability in such medium to large size applications. The nonaqueous electrolyte battery is further required to have high input-and-output characteristics.
Examples of nonaqueous electrolyte batteries having excellent life characteristics and high stability include a nonaqueous electrolyte battery in which a lithium titanate having a spinel-type crystal structure is used in a negative electrode. The lithium titanate having the spinel-type crystal structure has a high lithium insertion-and-extraction potential of approximately 1.55 V (vs. Li/Li+). Therefore, a battery voltage of a nonaqueous electrolyte battery using the lithium titanate having the spinel-type crystal structure in a negative electrode is low. Further, the lithium titanate having the spinel-type crystal structure is characterized in that in the lithium insertion-and-extraction potential ranges, it exhibits a very small change in a potential accompanying a change in a state-of-charge. That is, each of the charge and discharge curves of the lithium titanate having the spinel-type crystal structure includes a flat portion of a potential within the lithium insertion-and-extraction potential range.
In such a nonaqueous electrolyte battery, the life characteristics is required to be further improved.